GRB 180703A

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
Fermi/LAT GRB 180703A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00070

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

J. L. Racusin (NASA/GSFC), M. Crnogor��evi�� (UMD), M. Axelsson (KTH and Stockholm Univ.), 
A. Barker (George Washington), G. Vianello (Stanford), and M. Arimoto (Kanazawa University), 
report on behalf of the Fermi-LAT team:

At 21:01:40.50 on July, 03, 2018 Fermi-LAT detected high-energy emission from GRB 180703A, 
which was also detected by Fermi-GBM (trigger 552344505 / 180703876).

The best LAT on-ground location is found to be
RA, Dec = 6.54, -67.1 (J2000)
with an error radius of 0.3 deg (90% containment, statistical error only).

This was 48 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally 
correlated with the trigger with high significance.

The highest-energy photon is a ~930 MeV event which is observed at 40 seconds after the GBM trigger.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is Judith Racusin (judith.racusin@nasa.gov).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater 
than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and 
many scientific institutions across France, Italy, Japan and Sweden.

S.L. Gibson (U. Leicester), Z. Liu (NAOC / U. Leicester), P. D'Avanzo
(INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), S. J. LaPorte
(PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne
(U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 180703A (Racusin et al. GCN Circ. 22883
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 )
in a series of observations tiled on the sky. The total exposure time
is 2.0 ks, distributed over 4 tiles; the maximum exposure at a single
sky location was 863 s. The data were collected between T0+16.9 ks and
T0+29.0 ks, and are entirely in Photon Counting (PC) mode. 

One uncatalogued X-ray source has been detected, it is below the RASS
limit and shows no definitive signs of fading. Therefore, at the
present time we cannot confirm this as the afterglow. Details of this
source are given below:

Source 1:
  RA (J2000.0):  6.4693  =  00:25:52.63
  Dec (J2000.0): -67.1802  =  -67:10:48.7
  Error: 5.5 arcsec (radius, 90% conf.)
  Count-rate: 0.0207 [+0.0067, -0.0055] ct s^-1   
  Distance: 339 arcsec from Fermi/LAT position.
  Flux: (1.22 [+0.39, -0.32])e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)

A catalogued source was also detected.

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00070.

This circular is an official product of the Swift-XRT team.

C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara, D. Morris (U. of Virgin Islands) on behalf of a large collaboration report:

One of the LCO 1-m units at Sutherland Observatory (South Africa) began observing Fermi-LAT GRB 180703A (Racusin et al. GCN 22883
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 ) on July 04, 02:34 UT (5.5 hours after the GRB trigger time) with the SDSS i' filter. On the border of the Swift-XRT error circle of source S1 (Gibson et al. GCN 22891
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 ) we marginally detect an object at the following position:

RA(J2000)=  00:25:52.35
DEC(J2000)= -67:10:43.4

with an error radius of ~1" and a magnitude of i'=20.6 +- 0.3 at a mid time of 5.65 hours post GRB, as calibrated against nearby USNOB-UCAC4 stars.

S.Poolakkil and C. Meegan (both UAH) report on
behalf of the Fermi GBM Team:

"At 21:01:40.50 UT on 03 July 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180703A (trigger 552344505 / 180703876),
which was also detected by the Fermi LAT (Racusin et al. 2018, GCN 22883
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 ).
The GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight
at the GBM trigger time is 44 degrees.

The GBM light curve shows a single peak
with a duration (T90) of about 20.2 s (50-300 keV).
The time-averaged spectrum from T0-3.1 s to T0+25.6 s is
best fit by a Band function with Epeak = 360 +/- 33 keV,
alpha = -0.80 +/- 0.04 and beta = -1.95 +/- 0.08.

The event fluence (10-1000 keV) in this time interval is
(2.001 +/- 0.043)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.52 s in the 10-1000 keV band
is 11.1 +/- 0.25 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

S.W.K. Emery (UCL-MSSL) and E. Sonbas (Adiyaman Univ.)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180703A
17269 s after the Fermi/LAT trigger (Racusin et al. GCN Circ. 22883
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 ).
No optical afterglow consistent with the XRT position of the
uncatalogued X-ray source, source 1 (Gibson et al. GCN Circ. 22891
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 )
or the position from LCO Sutherland (Guidorzi et al. GCN Circ. 22892
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 )
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
exposures at the position of source 1 are:

Filter      T_start(s)   T_stop(s)      Exp(s)         Mag

b             17353         28862           47         >19.2
u             17323         28834          116         >19.5
uvw1          17269         28807          234         >19.8
uvw2          17384         28917           97         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).

V. Sharma, A. Vibhute and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:

Analysis of Astrosat CZTI data showed the detection of a long GRB 180703A, which was also detected by Swift (Evans P. A. et al., GCN 22882
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 ), Fermi-LAT (Racusin J. L. et al., GCN 22883
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 ), Swift-XRT (Gibson S. L. et al., GCN 22891
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 ) and Fermi-GBM (Poolakkil S. et al., GCN 22896
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 ).

The source was clearly detected in the 40-200 keV energy range. The light curve shows a single peak of emission with peak at 21:01:44.5 UT, ~4 s after the GBM trigger. The measured peak count rate is 277.3 cts/s above the background in combined data of four quadrants, with a total of 2182 cts. The local mean background count rate was 519.6 cts/s. Using cumulative rates, we measure a T90 of 20.9 s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin,
and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team,

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long duration GRB 180703A
(Fermi-LAT detection: Racusin et al., GCN Circ. 22883
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 ;
Fermi-GBM detection: Poolakkil and Meegan, GCN Circ. 22896
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 ;
AstroSat CZTI detection: Sharma et al., GCN Circ. 22900
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 )
was detected by Fermi (GBM trigger 552344505), Konus-Wind,
INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), and Swift (BAT),
at about 75700 s UT (21:01:40). The burst was outside the
coded field of view of the BAT.

We have triangulated it to a Konus-HEND annulus centered at
RA(2000)=312.437 deg (20h 49m 45s)  Dec(2000)=-22.995 deg (-22d 59' 40"),
whose radius is 54.738 +/- 1.217 deg (3 sigma).

The annulus is consistent with, but does not reduce the area of, the LAT
position reported by Racusin et al. (GCN Circ. 22883
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 ).

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB180703_T75705/IPN

V. Lipunov, E. Gorbovskoy, V.Kornilov,  N.Tiurina, A.Kuznetsov, V.Chazov,
I. Gorbunov, D. Vlasenko, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov
Lomonosov Moscow State University,SAI

D. Buckley,
South African Astronomical Observatory (SAAO)

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias (IAC)

A. Tlatov, V.Senik, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory

R. Podesta, F. Podesta, C. Lopez, C.Francile
Observatorio Astronomico Felix Aguilar (OAFA)

H.Levato,
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University (ISU)

A. Gabovich, V. Yurkov, Yu. Sergienko
Blagoveschensk Educational State University (BSPU)
MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru, 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in 
South Africa (South African Astronomical Observatory) was pointed to the 
GRB180703A (Poolakkil et al., GCN Circ #22896
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 ) 17 sec after notice time 
and 576 sec after trigger time at 
2018-07-03 21:11:17 UT. On our first (120s exposure)  set we not  found
optical transient within FERMI error-box (ra=349.946 dec=-65.5794 r=1.62) 
brighter then 18.0.

MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru, 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in 
South Africa (South African Astronomical Observatory) was pointed to the 
GRB180703A (Racusin et al., GCN Circ #22883
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 ) 14961 sec after trigger time 
at  2018-07-04 01:11:02 UT . On our first (180s exposure)  set we  do not 
found  optical transients within LAT error-box (ra=6.54 dec=-67.09 
r=0.3)  brighter then 18.3.

The observations made on zenit distance = 44 degrees, galaxy latitude b = 
-50 degree.
The moon (72 % bright part) is 55 degrees above the horizon. The distance 
between  moon and  object is 60
The sun  altitude  is -55.4 degree.
The object can be observed till sunrise at 2018-07-04 05:38:26

MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru, 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in 
Argentina (OAFA observatory of San Juan National University) was pointed 
to the  GRB180703A 14975 sec after trigger 
time at 2018-07-04 01:11:15 UT. On our first (180s exposure)  set we 
found 6 optical transient within LAT error-box (ra=6.5375 dec=-67.0894 
r=0.3039) brighter then 14.7.


The observations made on zenit distance = 76 degrees, galaxy latitude b = 
-50 degree.
The moon (72 % bright part) below the horizon (The altitude of the Moon is 
-18 degree ).
The sun  altitude  is -43.1 degree.
The object can be observed till sunrise at 2018-07-04 11:36:37


The visibility GRB error box (coord: 349.9500 -65.5800 error_box: 0.3) 
at trigger time at different MASTER sites:


obj: -42.33 sun: -21.55 - Tavrida (Crimea, Russia) 
obj: -41.44 sun: -11.38 - IAC, Teide, (Tenerife, Spain)
obj:  28.43 sun: -66.35 - SAAO (Sutherland, SA) 
obj: -31.89 sun: -23.27 - Kislovodsk (Russia)
obj: -38.98 sun: -9.15 -  Ural(Kourovka, Russia)
obj: -27.62 sun:  0.11 -  Tunka (near Baykal Lake, Russia) 
obj: -26.46 sun: 12.65 -  Amur(Blagoveschensk)
obj:  7.39 sun:  7.00 -   OAFA (Argentina)

The message may be cited.

D. Frederiks, S. Golenetskii, R.Aptekar, A. Kozlova,
A.Lysenko,  D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 180703A (IPN Triangulation: Hurley et al., GCN 22925
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 ;
Fermi-LAT detection: Racusin et al., GCN 22883
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 ;
Fermi-GBM detection: Poolakkil & Meegan, GCN 22896
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 )
triggered Konus-Wind at T0=75705.256 s UT (21:01:45.256)/

The burst light curve shows a single, FRED-like pulse
with a total duration of ~50 s. Also, there is a weak
count rate increase in the softest KW light curve around T0 + 170 s.
The emission in the main peak is seen up to ~10 MeV.

As observed by Konus-Wind, the burst had a fluence of
(4.1 �� 1.0)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+1.728, of (8.9 �� 1.3)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+49.408 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.85 (-0.21,+0.33),
the high energy photon index beta = -1.89 (-0.37,+0.19),
the peak energy Ep = 367 (-136,+196) keV,
chi2 = 89/97 dof.

The spectrum near the peak count rate (measured from T0
to T0+8.448 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.73 (-0.17,+0.20),
the high energy photon index beta = -1.90 (-0.22,+0.13),
the peak energy Ep = 407 (-97,+147) keV,
chi2 = 88/97 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180703_T75705/

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.

S.L. Gibson (U. Leicester), Z. Liu (NAOC / U. Leicester), P. D'Avanzo
(INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), S. J. LaPorte
(PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne
(U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:

Swift-XRT has conducted further observations of the field of the
Fermi/LAT-detected burst GRB 180703A (Racusin et al. GCN Circ. 22883
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 ).
The observations now extend from T0+17.3 ks to T0+263.7 ks. The source
previously reported by Gibson et al. (GCN Circ. 22891
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 ), "Source 1", is 
believed to be the afterglow.  The position of this source is RA,
Dec=6.4699, -67.1802 which is equivalent to:

RA (J2000): 00:25:52.79
Dec(J2000): -67:10:48.7

with an uncertainty of 4.8 arcsec (radius, 90% confidence).  This
position is 5.7 arcmin from the Fermi/LAT position.  The source is
fading with alpha >0.8.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020797.
The results of the full analysis of the tiled XRT observations are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00070.

This circular is an official product of the Swift-XRT team.

C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell 
(U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara, 
D. Morris (U. of Virgin Islands) on behalf of a large collaboration report:

We observed Fermi-LAT GRB 180703A (Racusin et al. GCN 22883
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 ) with the 
LCO 2-m unit in Hawaii (former FTN) on July 12, 17:46 UT (8.9 days after 
the GRB trigger time) with the SDSS i' filter. We do not detect the 
optical candidate (Guidorzi et al. GCN 22892
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 ) found on the border of the 
Swift-XRT error circle of the confirmed X-ray afterglow (Gibson et al. 
GCN 22931
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 ) down to a limit magnitude of i'> 22.0 with a 5x120s exposure. 
We therefore confirm the nature of optical afterglow of the candidate. A 
comparison between the images taken at both epochs is available at the 
link below.

http://www.fe.infn.it/u/guidorzi/new_guidorzi_files/180703A_OT.png

L. Izzo (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), P. Schady (U. Bath), D. B. Malesani (DAWN/NBI and DARK/NBI), D. A. Kann (HETH/IAA-CSIC), C. Kouveliotou (GWU), V. D���Elia (SSDC) and N. R. Tanvir (U. Leicester) report on behalf of the Stargate collaboration:

We have analysed the data obtained using the MUSE instrument, mounted on the ESO VLT UT4 (Yepun) telescope in Paranal, of the Fermi GRB 180703A (Racusin et al., GCN #22883
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 ; Poolakkil &  Meegan, GCN #22896
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 ). MUSE is an integral-field-unit spectrograph which covers a field of view of up to ~1 arcmin**2. Our observations started on 2018 July 04 at 07:53:56 UT, 10.92 hr after the GRB detection, and consisted of four exposures of 250 s each.

When we integrate the data cube along the full MUSE wavelength range, we detect a source within the uncertainty of the Swift/XRT afterglow position (Gibson et al., GCN #22891
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 ), and consistent with the position of the reported optical counterpart (Guidorzi et al., GCN #22892
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 , #22944
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 ). We extracted a spectrum of this source within the wavelength range 4750-9350 AA. The spectrum is noisy, and we cannot confirm continuum afterglow emission. However, we identify three strong emission lines which can be consistently interpreted as [O III] 4960,5008 AA and [O II] 3727/29 AA at a common redshift of z = 0.6678. Given the spatial coincidence with the optical counterpart, we propose that these features come from the GRB host galaxy and we conclude that this is the redshift of GRB 180703A.

We acknowledge support from the ESO observing staff in Paranal, in particular Andrea Mehner.